


Mabelchu

by PanPacificPines



Category: Gravity Falls
Genre: Cosplay, F/M, Shrinking
Language: English
Status: Completed
Published: 2016-02-03
Updated: 2016-02-03
Packaged: 2018-05-18 00:23:54
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,697
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5890888
Author URL: https://archiveofourown.org/users/PanPacificPines/pseuds/PanPacificPines
Summary: <blockquote class="userstuff">
              <p>This fic was inspired by the series of Pikachu Mabel pictures done by flasho-d on tumblr and yaschiri also on tumblr held me at gunpoint and kidnapped my family to force me to write it. So they should get some of the credit/blame. </p>
<p>Mabel, inspired by some pokémon fanart she found online decided to make a sexy pikachu cosplay and prank her brother with it. The results were somewhat unexpected. </p>
<p>-Note- It's not tagged in the Pokémon fandom because really, I don't think it belongs there.</p>
            </blockquote>





	Mabelchu

“Oh my freakin’ god! That’s so adorbs-balls cute!” Mabel clicked through image after image in a gallery of Pokémon cosplays and fan art. There were plenty of Ash and Misty couple cosplays and a few even had a toddler dressed up as a Pikachu or Pichu. There were sexy costumes and fantasy armor sets and a whole set of Eevee evolution girls in bikinis. She kept coming back to one piece of fan art though. She opened it in a new tab to keep it up even after having moved on from the article. It wasn’t just one thing that grabbed her attention, it was everything.  
“I could totally do that.” She thought to herself over and over again. 

She’d thought she had moved on, read other articles, watched other videos on makeup and blacksmithing. Her mind kept coming back to the image though. The girl could have practically been her. Just change the hair a bit, and maybe she wasn’t quite the exact same body type, but it was perfect otherwise. For probably the thirtieth time she found her mouse hovering over the tab and clicking. She could have been a playboy bunny, but the ears were yellow with brown tips and the one piece matched. There was even a tail on the back like the signature playboy bunny tail, except of course that bit was Pikachu’d up as well. 

It might have ended at fantasy but for the set of shopping tabs she opened up, just to see.  
“Okay, Mabel-Grabel, there’s no way we’re gonna- Damn.” There it was. The exact bathing suit she was looking for in yellow. She could have made it herself, but then she would have had the excuse that it was too much effort. “…Well now I just have to. Shit.” Almost against her will her hands propelled her into action, seeking out pencil and paper, mapping out the costume details. Her little project wouldn’t even cost her that much. She had a fifty percent off coupon that she could use for matching fabric at the local sewing supply store. 

“Damn it. Everything’s falling into place here. Oh, and a five dollar taser with free shipping. Crap. Well, now I have to be a PokéMabel.” A few clicks later a word document was open and several dozen costume projects filled the numbered list. PikaMabel found its way atop the heap at number one, pushing each of the other projects down by one. “Ugh. I am the worst.”

In the coming days she was almost able to put her new project out of her mind for even minutes at a time. Though that brief respite only came after sketching up a plan for a knit matching sweater with an over-sized neck hole so the sleeves would drape rakishly down past her shoulder. 

When the shipments showed up a few days later the whole outfit was done in the span of a single afternoon. Fabric paint, wire, thread and fabric came together under her skilled hands in no time at all. Connecting the tail to the bathing suit without it chafing had been the hard part, but the headband that connected the ears was easily concealed under her cascading brown locks. A generous dab of blush on each cheek, some yellow shadow above each eye, and the outfit was complete. A full length mirror hung on the back of her bedroom door and she modeled for herself in it. Sticking out her butt and tongue, holding up the peace symbol and winking an eye she gloried in how well it came together.  
“Okay, how do I use this to torment the bro-kémon master Dipster?”

Mabel tapped the taser to her lips as she thought and a wicked grin popped up on her face before fading back away.  
“No, can’t do that. If I go all stranger danger on Dippiedoodle I’m definitely grounded.” She turned it over, literally and figuratively both. There’s definitely a prank there waiting to happen, but it was just too big the way it was. A smaller shock would do it. The wicked grin resurfaced almost immediately as an evil plan came to mind.

Friday was date night for their parents so that’d be the right day for it. Dipper would hole up in his room except for food and when they’d have a movie night scheduled. She’d have to time it right. 

Mabel rummaged around in her closet for her adventure chest and pulled out the big solid box after tossing out the heaps of clothes and detritus that’d been piled on it. The old fashioned leather and brass trunk had a matching twin in her brother’s room and in them were various treasures from their summers in Gravity Falls. She extracted an unassuming little black velvet bag from the trunk and dumped the contents out on her bed. 

Crystals of various sizes spilled out on her blanket. Light seemed to bend around them, like they almost didn’t want you looking directly at them. Even still, if you forced yourself to do so you got the feeling like you were looking through a pair of red and blue 3D glasses. Mabel shook off the dizziness the things always gave her since she couldn’t help but stare and picked out a crystal fragment about the size of a dime and shut the rest away back in her trunk. 

It was a simple matter of rigging up the crystal to a pocket sized led flashlight that she could work both in Mabel classic and Mabel mini sizes. Gummy Koalas were great when you could look ‘em eye to eye, but she had no plans of getting stuck that size again. She measured herself against the door frame to make sure she’d get the height right and practiced the ray on both shrink and reverse a couple times to make sure it was working right. Then it was just a matter of waiting again until Friday rolled around. 

Once it did she planted the idea to order pizza in their parents head for them before they went out on their date. Pineapple and Mushroom was her choice and Boring Sausage and pepperoni for her brother. He didn’t even put sprinkles on his, the doof. Mabel threw on the costume, adjuster her hair over the headband and applied her makeup. She took a few selfies to post later after she surprised her bromigo. When the door bell rang signifying the arrival of the delivery guy she locked her door and hit play on an extra loud video.

After another ring of the bell she could hear her brother complaining from across the hall.  
“Mabel! Hey! The pizza guy’s here! ...Heeeey! Damnit.” The rest was unintelligible grumbling from outside her down and then footsteps on the stairs. She paused the video, clicked her light switch off and dashed across to her brother’s room. Mabel sat on the edge of Dipper’s bed and hit herself with the shrink ray until she was no more than a foot tall. Then she just tucked the shrink ray under his pillow and waited.

“Maaaabel! Food’s here! Mabel?” She could hear her door open and close again, this is it. “Where the hell is-?” The moment the bedroom door opened Mabel jumped up and shouted in an especially high pitch thanks to her size.  
“Mabelchuu!”  
“Holy crap!” Dipper shrieked like some sort of kitten-man, throwing his paper plate and pizza across the room.  
“Chuuu” She chirped and giggled, sitting how one might picture a cat doing, while quirking her head to the side. Hand to his heart Dipper recovered his list slice, inspecting it for hair and whatever other flotsam might be clinging to it.  
“Jesus Mabe, you take your little jokes too far. I’m gonna be the only teenager on earth with grey hair and a heart palpitation thanks to you.  
“Chu!” She pouted huffily. 

“Also! What if Mom and Dad had been home? Had you even thought of that? Jeeze, you can be so irresponsible sometimes. You know we’re supposed to keep the occult stuff from them. They couldn’t handle it!”  
“Chuu, Mabel! Mabelchuu!” She furrowed her brow and crossed her arms, all of which roughly translated to “Hey! I put more thought into this than that! You always think I’m irresponsible, you butt!”  
“Also, how long do you plan on doing that for?” Dipper plopped down on his computer chair and rolled it over to her, taking a bite from his pizza.  
“Mabel?” Quirking her head to the side, she put a finger to her lips, trying to look quizzical.

“Yeah, that.” He replied. “That talking like a Pokémon thing. Have you had your fun yet?  
“May! Chubel!” She shouted in response.  
“Okay, well that’s getting annoying. Alright, where’s the shrink ray? I have homework to do.”  
“Chuu!” She pouted again before sticking her tongue out at him.  
“Hey, come on. This isn’t fair. I can’t just leave you like that.” Mabel responded to his reasoning by motioning with her finger for him to get closer. Against his better judgment he leaned down closer to her and she bit him on the tip of the nose with a “Chu!”

“Gah!” He jumped back and clamped a hand over his nose. “Okay fine! We’ll leave you that size and see how you like it! She giggled to herself with plenty of “Chuus” thrown in for good measure. Though when he responded by turning his chair towards his computer to work on homework Mabel immediately found herself bored and wanting attention. So she ran around in circles on his bed and thrashed at his sheets and pillows when he didn’t respond. Frustrated she strained and struggled to actually pull the sheets up and toss a pillow over the side of the bed. Though she’d forgotten that the flashlight had been tucked under it so when the pillow hit the ground so did it. The sound caught Dipper’s attention and she snatched it up.

“Aha! I knew I could use your ADHD to my advantage!” He teased her by dangling it just over her head. “I guess your play time is over now.” Her competitive spirit got the better of her and she responded by clicking her taser on and zapping his hand with it. He recoiled and sucked on the spot she’d hit to numb the pain a bit. It wasn’t a bad shock, but the surprise hit him as though it’d been a fork in a toaster. “Okay, that’s it!” He set the led flashlight down angrily on his bookshelf and snatched the taser away from her as well, plonking it down next to the shrink ray. She’d been expecting maybe to be sprayed with a bottle of water for her antics like they use when their cat misbehaves, but her twin apparently had another punishment in mind. 

He hauled her up bodily in one hand, gripping tight enough to make any struggling futile and smacked her squarely on the ass. She wriggled and fought at first but the impact left her dumbfounded. The first smack was followed up by another, and then another. It stung but damn if it didn’t feel right. She felt the heat rise up in her face and a whole range of new feelings crept around in her belly. He set her back down on the bed and said something about behaving and growing her back to normal size. Whatever it was she wasn’t paying much attention. Mabel simply answered with a “Belchu” and nodded her head. 

She sat in total silence for a while after that, shifting her thighs around a bit to feel the numb stinging sensation just a bit longer. She wasn’t a virgin, or even a stranger to the idea that some people liked being spanked but that idea had never clicked with her before. It never seemed “Mabel” enough. She still wasn’t sure, especially considering who it’d been that just done it. Dipper didn’t have sex on the brain when he smacked her butt. He just wanted her to behave and being just a bit smaller than their cat must have put the idea in his head to treat her like a kid; though neither of them had ever been spanked as children. 

She sat in a sort of puzzled daze, mulling over her feelings. Was she really turned on by her brother, probably six times taller than her, giving her a spanking? What if she was? Was that even okay? People get judged pretty harshly for that sort of behavior. Finally Mabel decided that since she was dressed up like a Pokémon, less than a foot tall and had gone to hell and back almost literally with her brother, normal was sort of a relative term. Besides, she didn’t even know for sure if he did it for her. Only way to tell was to repeat the experiment and see if the results replicated. 

“Did I just nerd talk inside my own head?”She thought. “Okay. I need to figure this biz out.” The mature thing might have been to ask to be grown back to normal size and have a heart to heart with her brother about what she thought she was feeling and see how he felt on the matter. Mabel didn’t go in for ‘the mature thing to do’ though. So naturally the way to go was to wreck whatever she could. 

She ran in circles again, screaming her little head off. She gnawed on his blankets and kicked his wall but she was so little that honestly her destructive rampage was more hamster and less hostile. Dipper didn’t seem to notice, or at least he didn’t pay her any mind if he did. So she tossed what blanket she could over the edge of the bed and used it to climb down. Then she scurried over to Dipper and scaled his pant leg. He didn’t make it easy though, as always he was ticklish and fidgety. 

She persevered and scrambled up the length of his leg to stand on his knee, hands on her hips and a grumpy expression on her face.  
“What’s got you so cranky?” He chuckled, patting her on the head. “Don’t tell me you’re still upset about me taking your toy away.” She shook her head. “Okay, what then?”  
“Chuuuu! BelMabel chuu!” She ranted, almost as though she expected him to understand, even punctuating with arm gestures. He just patted her on the head again and continued clacking away at his keyboard. It was time for extreme measures. She decided that provoking him for attention would be a double pleasure and leapt from her perch on his knee and tackled his crotch.

She couldn’t have weighed more than a few pounds, but it was enough. He bolted upright and sent her crashing to the ground. Though he didn’t seem to be in much pain when he picked her up off the carpet, though still hunched over and asked in a panic “Mabel, are you okay? I’m so sorry; I didn’t mean to drop you!”  
She rubbed her head and responded with a weary and bruised “Chuuu” and reflected that her plan could have gone better. He set her back onto his bed and did his best to inspect her for injuries. 

“Maybe I should grow you back to normal size now.” Dipper said, reaching for the flashlight on his shelf.  
“Chuu!” Mabel shouted, shaking her head vigorously before immediately regretting that decision and clutching at her head to keep her brain from rattling around. After that fall she wasn’t entirely sure she still wanted to test out her spanking theory. Since she refused to use real words until she was out of costume she also couldn’t just ask for it. Though how exactly does one just blurt out “hey bro, can you smack my ass a few more times? I think I liked it.” Not likely. 

“Okay, okay, I guess you can stay small for a while if you want.” He said this while rubbing her cheek gently with the tip of his finger. “Mom and Dad will still be gone for a while. But I’m making you big again before they come back.” Then he gave her a little smile and scratched her behind one of her false ears.  
“Ooh, this I can get behind.” Mabel thought. “It’s not what I was after, but it’ll do.” She happily leaned into her brother’s gentle caress and nuzzled into his hand.  
“Okay, you be a good girl.” He made to take his hand back to finish his homework but she grabbed onto his thumb and whined. “Oh, alright, I suppose I can type with one hand…you’d better not make a joke about that or the petting stops. Got that?” She nodded and happily accepted the approving back scratch that followed. 

She leaned into it like a bear on a tree. Nothing could quite describe the feeling of it either. As Dipper hunted and pecked on his keyboard at whatever he was doing his left hand became a little lazy with the petting. It mostly just waggled the same couple fingers back and forth, leaving her to decide which body parts would be stroked. He must not have been paying close attention, because when she decided she wanted to try a belly rub his fingers grazed over her breasts more than once. She certainly didn’t mind though. After all, minutes ago she was trying to get him to spank her.

It sent pleasant, cool little shivers through her body whenever his touch happens to make that mistake. Then shock of all shocks a rogue finger flicks out a bit farther than normal and brushes her between her legs, bringing a little squeal out of her. Immediately Mabel clamped a hand over her mouth but Dipper didn’t seem to notice her squeak.  
“Damn, Dip. What’re you tryina do to me?” She thought, while trying surreptitiously to scoot her body up a little further so that he might make the same mistake again. She felt a bit guilty about it, but did it just the same. After a few moments of wriggling there it was again. The rough texture of her twin’s finger pad was stroking against her most sensitive spot. 

Mabel gripped down on her brother’s enormous hand and ground her hips into it. She shuddered and bit down on her lip trying to control the spasms the act brought out of her as she gripped his finger between her thighs. The bathing suit she designed her costume around was designed to look good, not to stay on through such manipulations so it was no surprise when her breasts came free as her hips worked over her twin’s finger. She didn’t care anymore though. The wrongness, the taboo of it all only fueled her fire and urged her on. 

The vast difference in their size magnified Dipper’s relative strength tremendously and didn’t make for the most gentle sensation but she loved it. Riding on the edge of desire and ecstasy she fought as hard as she could to keep from squealing. If Dipper was really so distracted she was fine letting him stay that way. Maybe he was choosing to seem ignorant about what she was doing, either way she was getting closer, and closer. Her thighs practically dripped with her wetness as she ran her slit over her twin while his finger continued to stroke away. 

Whether it was the way her body had adjusted to the motions or if Dipper’s movements had adjusted to her she couldn’t tell or care but it started hitting her just right and she pressed her cheek down into his wrist, panting, gasping hot breaths into his skin. Mabel couldn’t handle it anymore and gave up all pretense and twisted one of her freed nipples. Her eyes clenched shut and her body shook, thighs tightened down on her brother’s digit while the most intense orgasm she’d yet experienced racked her body. 

“Chuuuuuuuu” She squealed with a breathy satisfied moan, almost against her will. Dipper’s head snapped around, a horrified expression on his face and her heart sank. She hadn’t really considered the consequences before that second.  
“Oh my god, Mabel, I’m so sorry, I-I didn’t know what- I didn’t mean to-!” panicked, he tried to pull his hand back, but she gripped his thumb and held it in place. She couldn’t let him blame himself. To punctuate her point she ground herself into him again even as she straightened her back up, choosing not to fix the cups back over her chest.  
“Chu!” Even with the little exclamation her skin was covered in goosebumps and her blood seemed to run cold. If he wanted to hate her for this, it was his right. 

“I- I don’t understand Mabes. You- please use real words here. I kinda feel like – I think maybe we should- Damn I don’t know…” While her brother babbled and stammered she realized something. He didn’t seem to hate her like she thought he might, far from it. He was blushing!  
“Okay, embarrassment and Dipper sorta go hand in hand but shouldn’t he feel disgusted?” Instinct drew her eyes down and sure enough, there was a very noticeable tent in her brother’s pants. He was trying to hide it but it was there. She sat down on his palm and held onto his thumb, motioning for him to pick her up.  
“Chu!”  
“Uh, o-okay.” His heart was beating so quickly and she could feel it even through his palm. He obeyed the implied command and held her up at face level and she planted a kiss on the tip of his nose before pointing down.

“Are you saying it’s o-okay?” when he didn’t seem to understand the intention she hopped from his hand to his chest and slid down his shirt onto his lap. He tried to cross his legs and hunch over in an attempt to deny the existence of his excitement but two firm little hands gripping onto it him stopped him in his tracks.  
“Wh-Mabel, what are you-?” The two same little hands determinately tugged on his zipper, yanking it down revealing the bulge in his now very tight white underwear. Mabel then nuzzled her cheek into the firmness she found there. Despite their size different he seemed all too willing to let her control where they’d be taking this. When she pressed a hand to the button of his pants he immediately complied by unfastening it for her, leaning back to see just what she’d do. 

Mabel pulled back the flaps of fabric caging in her brother and out he came. To say it seemed big from her angle would have been a fairly massive understatement. She stood there taking in the whole thing. She’d never been this close to…well... Her mind was set. Sure, maybe this was weird, staring down the business end of her brother’s big dipper, but it felt right to make him feel good like he’d done for her. There was a musky scent, sorta manlier than she’d expected from him, especially considering how beet red his face was.

“Well, here we go, no turning back now. He’s all stiff and excited. Ooh, it twitched.” She kissed the tip of it and it twitched again, swelling up even more before settling back down a couple seconds later. “Oh, we’re responsive, aren’t we?” Determined to stimulate her brother as much as he’d done for her she ran one hand up and down his length while the other slid around to caress the underside of its head. 

Dipper’s body responded to her, his eyes clenched shut as he sharply took in a breath. His arms and legs stiffened when she touched him. All sorts of interesting grunts and low moans came out of him depending on where she moved her delicate, nimble hands, almost as though he were an instrument responding to a skilled musician. She nibbled lightly on the squishy flesh of the head and licked up the beads of moisture gathering at its tip all the while running her fingers up, down and around him. 

She could feel her own wetness building up again even as her twin’s breathing grew faster and faster under her manipulations. So she knelt down on his thighs and pulled the fabric of her swimsuit to the side and ran her bare skin over his. Sliding her moistened slit up and down his throbbing member, her hips bucked as waves passed through both of their bodies. It seemed almost unfathomable but the raw exhilaration brought her right back to the peak of sheer bodily excitement she’d experienced minutes ago. 

The fact that they were enjoying the sinful thrill together just made it better. She was being selfish again, she thought, riding the edge of both pleasure and her twin brother, coming closer and closer to climax again so she thought she’d throw him a metaphorical bone. She threw herself completely into it, really digging in, squeezing him between her thighs again as she extracted every bit of sensation from him as she could until finally she felt the peak come over her and she called out his name.  
“D-Dipperrr!” Their bodies tensed together as her body pressed around him, racked with pleasure. Immediately as the wave passed over her she dedicated her full attention to him, licking at the underside, running her hands along the shaft, even nibbling at the rim of the head. 

After just a bit of this manipulation he seemed to swell up again and he called out her name as well, pulling her away and just barely pressing a napkin over the tip in time.  
“Oh – Oh fuck, Mabel, god damn…” He panted out, cleaning up the mess she’d helped him make. Though since he’d only just pulled her away, when his attention wasn’t completely focused on her she lapped up a spare drop that rose to the top with a “Chuu” to punctuate it.  
“Nnggg-G-god Mabel. Jeeze, a guy can only take so much.” 

He plucked her up and placed her on the bed. Without giving her a chance to complain he flicked the crystal over on the flashlight and grew her to about what he thought her full height should be.  
“So…are you gonna just make ‘chuu chuu’ sounds at me or are we gonna talk about what just happened?” She giggled and licked the tip of his nose.  
“Yeah, Dipper. We can talk about it. But I have a counter offer.”  
“Okay, shoot.”  
“I dunno, didn’t you just do that?” She grinned, poking the tip of his still erect symbol of their affection.  
“M-Mabel! Hey!” Dipper struggled to hide it back in his underwear and zip up his pants to prevent more of this new brand of Mabel mischief. “Just lay it- Tell me what your offer is.”  
“Well, mister Big Dipper” She let the capitol letters leak into her voice “Mom and Dad are going to be home in, what, an hour? Maybe less? I think I need to change into something a little less ‘I just slid my pussy all up and down my brother’s dick’” She indicated the wet spot on her bathing suit and smiled at how his face turned from pink to crimson at her use of vocabulary. “Oh yeah, bro, that’s what happened. Anyway, I need to change and I think you maybe should air out the sweaty wild monkey smell in here. We’ll pretend like this didn’t happen when they show up. Then when they’re asleep…”

“Y-yeah?” His anticipation was practically a visible, physical force. “Then what?”  
“Then” she grabbed him by the collar of his shirt and pulled him in close “You’ve gotta tame this Poké-ass. You’re going to come into my room when you’re sure they’re asleep and you’re gonna fuck my brains out. Full size. Then if you want we can talk about this. You got that?” He just nodded his head dumbly, knowing full well that she was the one who’d caught him and if he was lucky there was an Ash Ketchum cosplay in his future.”


End file.
